Dimethyl sulfoxide distillation residue recovery system and recovery method thereof

Abstract

This invention provides a dimethyl sulfoxide (DMSO) distillation residue recovery system and method. The recovery system includes: a concentration vessel containing a stirrer, an inlet, a vapor outlet, and a waste discharge pipe. The inlet is connected to the residue outlet of the DMSO distillation vessel, and the waste discharge pipe has a slag outlet and a first liquid outlet; an evaporator-condenser connected to the vapor outlet to condense and liquefy the vaporized DMSO discharged from the concentration vessel, and has a second liquid outlet; and a condensate collection tank connected to both the first and second liquid outlets. This invention recovers the volatile DMSO and concentrate from the concentration vessel into the condensate collection tank, while the solid, harmless residue from the solid-liquid separation is discharged through the slag outlet. This achieves efficient recovery and treatment of the residue from the DMSO distillation vessel, resulting in pollution-free discharge and effectively improving the recovery rate of DMSO.

Description

Technical Field

[0001] This invention belongs to the field of dimethyl sulfoxide recycling technology, specifically relating to a dimethyl sulfoxide distillation residue recovery system and its recovery method. Background Technology

[0002] The production of polyacrylonitrile (PAC) carbon fiber generates a large amount of wastewater containing dimethyl sulfoxide (DMSO), acrylonitrile, water, and PAC oligomers. Currently, PAC carbon fiber manufacturers use multi-tower continuous distillation to separate the smaller molecules of acrylonitrile, DMSO, and water. However, the dimethyl sulfoxide distillation process also produces DMSO distillation residue, which contains decomposition products of DMSO, polymers, heavy components, salts, and particulate matter. This residue is difficult to recover and treat, and if not treated promptly, it can cause problems such as coking and blockage of the reboiler in the distillation tower. Currently, a large amount of DMSO distillation residue is collected in drums, with a DMSO content exceeding 90%. Treating this as hazardous waste at the factory not only incurs significant processing costs and wastes resources but also causes environmental pollution. Summary of the Invention

[0003] Therefore, the present invention provides a dimethyl sulfoxide distillation residue recovery system and method to solve the problem in related technologies where dimethyl sulfoxide distillation residue cannot be further refined and is directly discharged as waste, causing environmental pollution.

[0004] To address the above problems, the present invention provides a dimethyl sulfoxide distillation residue recovery system, comprising:

[0005] A concentration vessel containing a stirrer, the concentration vessel having a feed inlet, a gas phase outlet, and a waste discharge pipe, wherein the feed inlet is used to connect with the residual liquid outlet of a dimethyl sulfoxide distillation vessel, and the waste discharge pipe has a slag outlet and a first liquid outlet;

[0006] An evaporative condenser, which is connected to the gas phase outlet to condense and liquefy the gas phase dimethyl sulfoxide discharged from the concentration vessel, has a second drain port;

[0007] A condensate collection tank, which is connected to both the first drain port and the second drain port.

[0008] In some implementations...

[0009] The condensate collection tank has a third drain port, which is used to connect a pumping component to pump the condensate collected in the condensate collection tank to the dimethyl sulfoxide distillation vessel.

[0010] In some implementations...

[0011] The waste discharge pipe is located at the bottom of the concentration vessel, the waste discharge pipe is vertically arranged, the slag discharge port is located at the bottom end of the waste discharge pipe, and the first liquid discharge port is located on the side wall of the waste discharge pipe; and / or, it also includes a vacuum pump, which is connected to the evaporator condenser.

[0012] In some implementations...

[0013] The bottom of the concentration vessel is an inverted cone, and the waste discharge pipe is located at the apex of the cone.

[0014] In some implementations...

[0015] The stirrer includes a stirring frame, the bottom shape of which matches the shape of the bottom of the vessel.

[0016] In some implementations...

[0017] The stirring frame is provided with multiple scrapers at positions corresponding to the wall of the concentration vessel, and the distance between the scrapers and the vessel wall is no more than 50 mm; and / or, the scrapers are detachably connected to the stirring frame; and / or, the scrapers are made of stainless steel or polytetrafluoroethylene.

[0018] The present invention also provides a method for recovering dimethyl sulfoxide distillation residue, wherein the method is carried out using the above-mentioned dimethyl sulfoxide distillation residue recovery system, and the method includes:

[0019] The residual liquid from the dimethyl sulfoxide distillation vessel is transferred to the concentration vessel and the injection is stopped when the residual liquid level reaches a first preset height.

[0020] The vacuum level inside the concentration vessel is controlled to reach a first preset pressure value, and the temperature is controlled to be at a first preset temperature.

[0021] The stirrer is controlled to rotate at a first speed.

[0022] When the residual liquid level in the concentration vessel drops to the second preset height, demineralized water is introduced into the concentration vessel to separate the residual liquid into solid and liquid residues and concentrate.

[0023] After opening the slag discharge port to discharge the residue, open the first liquid discharge port to discharge the concentrate into the condensate collection tank.

[0024] In some implementations...

[0025] As the residual liquid level in the concentration vessel decreases, the rotational speed of the stirrer decreases; and / or, when the condensate collection tank has a third drain port and a pumping component is connected between the third drain port and the dimethyl sulfoxide distillation vessel, the pumping component is controlled to operate after the concentrate is discharged into the condensate collection tank; and / or, when the residual liquid level in the concentration vessel reaches a second preset height, the ambient pressure inside the concentration vessel is controlled to reach a second preset pressure value, the second preset pressure value being greater than the first preset pressure value.

[0026] In some implementations...

[0027] The total height of the internal space of the concentration vessel is L, the first rotation speed of the stirrer is V, and the real-time liquid level of the residual liquid in the concentration vessel is Ls. When 70%L < Ls ≤ 80%L, the stirrer rotates at a constant speed of V. When 50%L < Ls ≤ 70%L, the rotation speed of the stirrer decreases linearly from V to 50%V. When 20%L < Ls ≤ 50%L, the rotation speed of the stirrer decreases linearly from 50%V to 10%V. When 10%L < Ls ≤ 20%L, the stirrer rotates at a constant speed of 10%V.

[0028] In some implementations...

[0029] The first preset pressure value is 4 kPaA to 10 kPaA, the first preset temperature is 90℃ to 120℃, and the second preset pressure value is 0.05 MPa to 0.15 MPa; and / or, the first rotational speed is 100 rpm to 150 rpm, and the second rotational speed is 10 rpm to 15 rpm; and / or, the rate of decrease in the rotational speed of the stirrer when 50% L < L1 ≤ 80% L is greater than the rate of decrease in the rotational speed of the stirrer when 20% L < L2 ≤ 50% L; and / or, the first preset height is 80% L, and the second preset height is 10% L.

[0030] This invention provides a dimethyl sulfoxide (DMSO) distillation residue recovery system and method. On the one hand, DMSO volatilized in the concentration vessel is recovered to the condensate collection tank via the gas phase outlet. On the other hand, the concentrated liquid containing DMSO after solid-liquid separation is also recovered to the condensate collection tank via the first discharge port. The solid, harmless residue from the solid-liquid separation is discharged via the slag discharge port. This achieves efficient recovery and treatment of the residue from the DMSO distillation vessel, realizes pollution-free discharge, and effectively improves the recovery and utilization rate of DMSO. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the dimethyl sulfoxide distillation residue recovery system according to an embodiment of the present invention;

[0032] Figure 2 for Figure 1 A schematic diagram of the structure of a stirrer in a device;

[0033] Figure 3 for Figure 1 Another schematic diagram of the stirrer in the image;

[0034] Figure 4 This is the stirrer speed control curve in an embodiment of the present invention.

[0035] The reference numerals in the attached figures are as follows:

[0036] 1. Concentrator; 11. Gas discharge port; 12. Waste discharge pipe; 121. Slag discharge port; 122. First liquid discharge port; 13. Feed inlet; 2. Evaporator condenser; 21. Second liquid discharge port; 3. Condensate collection tank; 31. Third liquid discharge port; 4. Vacuum pump; 5. Stirrer; 51. Stirring frame; 511. Top frame; 512. Middle frame; 513. Bottom frame; 52. Scraper; 6. Heating jacket; 7. Liquid level sensor. Detailed Implementation

[0037] See also Figures 1 to 4As shown in the embodiment of the present invention, a dimethyl sulfoxide (DMSO) distillation residue recovery system is provided, comprising: a concentration vessel 1 having a stirrer 5, the concentration vessel 1 having a feed inlet 13, a gas phase outlet 11, and a waste discharge pipe 12, wherein the feed inlet 13 is connected to the residue outlet of the DMSO distillation vessel, and the waste discharge pipe 12 has a slag outlet 121 and a first liquid outlet 122; an evaporator condenser 2 connected to the gas phase outlet 11 to condense and liquefy the gaseous DMSO discharged from the concentration vessel 1, and having a second liquid outlet 21; and a condensate collection tank 3 connected to both the first liquid outlet 122 and the second liquid outlet 21. It is understood that the residue recovery system also includes a vacuum pump 4 for evacuating the internal environment of the concentration vessel 1 during the DMSO recovery process. The concentration vessel 1 also includes a heating element for heating the residue in the vessel to a suitable temperature to facilitate the evaporation of DMSO from the residue into a gas phase. In this technical solution, on the one hand, the dimethyl sulfoxide volatilized in the concentration vessel 1 is recovered to the condensate collection tank 3 via the gas phase discharge port 11. On the other hand, the concentrated liquid containing dimethyl sulfoxide after solid-liquid separation is also recovered to the condensate collection tank 3 via the first discharge port 122. The solid, harmless residue from the solid-liquid separation is discharged via the slag discharge port 121. This achieves efficient recovery and treatment of the residue from the dimethyl sulfoxide distillation vessel, resulting in pollution-free discharge and effectively improving the recovery rate of dimethyl sulfoxide. Experimental verification shows that the recovery rate of dimethyl sulfoxide can be increased by about 5% through the residue recovery system of this invention. It should be noted that the aforementioned harmless residue can be used as construction waste for landfilling, causing no pollution to the environment and being environmentally friendly. This residue mainly includes polymer carbides, calcium salts, magnesium salts, and soil particles. In terms of specific process treatment, after the residual liquid is concentrated to the target level (i.e., the liquid level is lower than the preset height), demineralized water is introduced into the concentration vessel 1 to dissolve part of the residual liquid adhering to the residue, thereby cleaning the residue. The density of the demineralized water after cleaning is lower than the density of the residue, so the residue is located below the solution. Based on this characteristic, the first drain port 122 in this invention is set above the slag discharge port 121 so that the residue at the bottom can be discharged first, and then the solution can be discharged from the first drain port 122 and recycled into the condensate collection tank 3.

[0038] The purpose of the aforementioned evaporator-condenser 2 is to condense the volatilized and recovered dimethyl sulfoxide into a liquid state, which is then collected and stored in the condensate collection tank 3, ensuring safety, reliability, and saving storage space. For details regarding the aforementioned heating components, please refer to [link to relevant documentation]. Figure 1As shown, a heating jacket 6 is installed around the vertical wall of the concentration vessel 1. It is filled with steam or oil at a certain pressure and temperature to heat the vertical wall of the concentration vessel 1, thereby transferring the heat to the residual liquid inside the vessel. In a specific embodiment, steam at 0.5–0.8 MPa is introduced into the heating jacket 6 to ensure that the temperature of the residual liquid inside the concentration vessel 1 is controlled below 120°C, preventing further decomposition and cracking of the distillation residue, which could lead to carbonization or explosion.

[0039] The dimethyl sulfoxide (solution) recovered in the condensate collection tank 3 can be independently subjected to subsequent distillation treatment to achieve the final efficient recovery of dimethyl sulfoxide. In a preferred embodiment, the condensate collection tank 3 has a third drain port 31, which is used to connect a pumping component to pump the condensate collected in the condensate collection tank 3 to the dimethyl sulfoxide distillation kettle. That is, in this technical solution, the dimethyl sulfoxide solution recovered in the condensate collection tank 3 is automatically pumped back to the dimethyl sulfoxide distillation kettle in the upstream process for distillation recovery through the pumping component, forming a recycling of dimethyl sulfoxide. The recovery rate is higher. Experimental verification shows that the recovery rate of dimethyl sulfoxide in the distillation stage is about 95%. After adopting the recovery system of the present invention, about 5% of the dimethyl sulfoxide carried away by the discharge of the distillation residue will also be recovered. Therefore, the recovery rate of dimethyl sulfoxide after the distillation residue treatment can reach more than 99%.

[0040] Waste discharge pipe 12 can be a pipe assembled from multiple different pipe sections or formed by integrated processing; see [link / reference]. Figure 1 As shown, the waste discharge pipe 12 is located at the bottom of the concentration vessel 1. In a preferred embodiment, the waste discharge pipe 12 is vertically arranged, with the slag discharge port 121 at the bottom end and the first liquid discharge port 122 located on the side wall of the waste discharge pipe 12. Since the weight of the solid residue formed during the concentration process is greater than that of the concentrated liquid phase, the liquid phase components will float on top of the solid residue. To accommodate this solid-liquid separation phenomenon, placing the slag discharge port 121 at the bottom end of the waste discharge pipe 12 and the first liquid discharge port 122 on the side wall of the waste discharge pipe 12 allows for convenient discharge of the lower-layer residue before the concentrated liquid is discharged through the first liquid discharge port 122. This method is simple and convenient. To facilitate the collection and guidance of the residue and concentrated liquid discharge, the bottom of the concentration vessel 1 is designed as an inverted cone (i.e., the longitudinal section is an inverted cone), with the waste discharge pipe 12 located at the apex of the cone.

[0041] The purpose of the aforementioned vacuum pump 4 is to change the pressure of the internal environment of the concentration vessel 1, such as to create a vacuum, so as to facilitate the volatilization of dimethyl sulfoxide. Of course, when necessary, the vacuum pump 4 can also create a positive pressure in the internal environment of the concentration vessel 1 to force the residue and concentrate to be discharged smoothly. In a preferred embodiment, the vacuum pump 4 is connected to the evaporator condenser 2. Specifically, the vacuum pump 4 is connected to the gas phase outlet of the evaporator condenser 2 so that while regulating the internal environment pressure of the concentration vessel 1, the evaporator 4 can guide the volatilized dimethyl sulfoxide into the evaporator condenser 2 for condensation and liquefaction during vacuuming.

[0042] See Figure 2 As shown, the stirrer 5 includes a stirring frame 51. The bottom shape of the stirring frame 51 matches the shape of the vessel bottom. That is, the concentration vessel 1 in this invention has a flat-topped, conical-bottom shape, and the outer shape of the stirring frame 51 is also designed to match this shape, so as to ensure sufficient and efficient stirring of the residual liquid and to ensure uniform heating of the residual liquid. See further details. Figure 2 As shown, multiple scrapers 52 are installed at positions corresponding to the walls of the concentration vessel 1 (including the positions corresponding to the vertical walls and the bottom conical walls of the vessel body) on the stirring frame 51. The distance between the scrapers 52 and the vessel wall is no greater than 50mm. Correspondingly, the distance between the outer edge of the stirring frame 51 and the corresponding vessel wall should be no greater than 100mm to prevent damage caused by excessive bending moment during the rotation of the stirrer 5 due to excessive extension length of the scrapers 52. The scrapers 52 and the stirring frame 51 are detachably connected, for example, by bolting. With this design, the stirring frame 51 and the scrapers 52 can be made of different materials. For example, the scrapers 52 can be made of stainless steel or polytetrafluoroethylene (PTFE). Stainless steel or PTFE scrapers 52 have certain strength and wear resistance, extending their service life and providing good resistance to high-temperature corrosion from dimethyl sulfoxide. Multiple scrapers 52 can be specifically provided. Figure 2 (Only one is shown schematically). Multiple scrapers 52 are arranged at certain intervals on the outer contour of the stirring frame 51 corresponding to the vessel wall, so as to scrape off the solid residue adhering to the vessel wall in a timely manner, ensuring timely and efficient heat transfer of the heating element. The aforementioned scrapers 52 are 4 or 6, 8, 10... even numbers of scrapers, and these scrapers are symmetrically and evenly distributed on both sides and bottom of the stirrer.

[0043] As another preferred implementation of the stirrer 5, the stirrer 5 is a top-down split assembly structure, see [link to relevant documentation]. Figure 3As shown, the stirring frame 51 includes a top frame 511, a middle frame 512, and a bottom frame 513 from top to bottom. The mechanical strength of the top frame 511, middle frame 512, and bottom frame 513 gradually increases, that is, the mechanical strength of the bottom frame 513 is higher than that of the middle frame 512, and the mechanical strength of the middle frame 512 is higher than that of the top frame 511. This design, with varying mechanical strengths at different heights, ensures that the mechanical strength of the stirring frame 51 matches the solid content of the residual liquid, guaranteeing the stirring effect while preventing damage to the stirring frame 51 and extending its service life. The stirring frame 51 also does not need to be entirely made of high-strength materials, reducing manufacturing costs. The aforementioned recycling system is stable, easy to operate, and safe and reliable. It is understood that the aforementioned mechanical strength refers to the maximum load that a material can withstand per unit area when subjected to external forces, generally expressed as bending strength, tensile strength, compressive strength, impact strength, etc. Meanwhile, the split-type agitator objectively increases the number of agitating elements, which can improve the agitation effect, ensure uniform mixing of the upper and lower liquid levels, and facilitate mass and heat transfer.

[0044] According to an embodiment of the present invention, a method for recovering dimethyl sulfoxide distillation residue is also provided. The method employs the aforementioned dimethyl sulfoxide distillation residue recovery system and includes:

[0045] S100, the residual liquid from the dimethyl sulfoxide distillation vessel is transferred to the concentration vessel 1 and the injection is stopped when the residual liquid level reaches the first preset height;

[0046] S200 controls the vacuum level inside the concentration vessel 1 to reach the first preset pressure value and the temperature to be at the first preset temperature.

[0047] S300, controls the stirrer 5 to rotate at the first speed;

[0048] S400, when the residual liquid level in the concentration vessel 1 (detected by the liquid level sensor 7 located in the concentration vessel 1) drops to the second preset height, demineralized water is introduced into the concentration vessel 1 to separate the residual liquid from the concentrate, forming a solid-liquid separation. The aforementioned demineralized water refers to groundwater that has undergone reverse osmosis, ion exchange, or other methods to remove suspended solids, colloids, calcium, magnesium, sodium, and other ions, forming pure water containing very little or no minerals. The demineralized water is miscible with dimethyl sulfoxide in the distillation residue, but insoluble with the polymers therein (i.e., the part that ultimately becomes solid).

[0049] S500, after opening the slag discharge port 121 to discharge the residue, open the first liquid discharge port 122 to discharge the concentrate into the condensate collection tank 3.

[0050] In this technical solution, the first preset pressure and temperature allow dimethyl sulfoxide (DMSO) in the residual liquid to volatilize efficiently, forming a gas phase that then enters the evaporator-condenser 2, condenses, and is recovered in the condensate collection tank 3. When the residual liquid level drops to a second preset height, demineralized water is introduced into the concentration vessel 1 to further clean the residue, significantly reducing the DMSO content in the residue. The DMSO absorbed by the demineralized water is then sent to the condensate collection tank 3 for recycling. Thus, the recycling method of this invention can recover both the volatilized gas phase DMSO and the DMSO in the concentrate, thereby improving the DMSO recovery rate. Furthermore, due to the cleaning effect of the demineralized water, the DMSO content in the residue is extremely low, reaching a harmless level, allowing the residue to be disposed of as construction waste through landfill, which is environmentally friendly.

[0051] When the condensate collection tank 3 has a third drain port 31 and a pumping component is connected between the third drain port 31 and the dimethyl sulfoxide distillation vessel, the pumping component is controlled to operate after the concentrate is discharged into the condensate collection tank 3. At this time, the dimethyl sulfoxide (containing demineralized water) recovered in the condensate collection tank 3 is pumped to the dimethyl sulfoxide distillation vessel in the upstream process for further distillation, making it easier to separate. Through this circulating distillation method, the recovery rate of dimethyl sulfoxide is guaranteed to be as high as 99% or more.

[0052] In a preferred embodiment, as the residual liquid level in the concentration vessel 1 decreases, the rotation speed of the stirrer 5 decreases. Specifically, as the concentration proceeds, the dimethyl sulfoxide component in the residual liquid in the concentration vessel 1 evaporates into a gas phase and is discharged from the vessel, causing the residual liquid level to gradually decrease. Meanwhile, the solid phase ratio in the residual liquid gradually increases as the residual liquid level decreases. The increased solid phase ratio leads to a higher residual liquid viscosity, resulting in greater stirring resistance. To prevent the drive motor of the stirrer 5 from tripping or even burning out due to excessive current, the rotation speed of the stirrer 5 is appropriately reduced in this invention. It should also be noted that a lower stirring speed can reduce the evaporation rate of the residual liquid at this time, preventing premature solidification of the residual liquid. This treatment allows the dimethyl sulfoxide in the residue to be recovered as much as possible through evaporation. Of course, when the solid phase ratio is large, stirring at a lower stirring speed can also prevent damage to the structure of the stirrer 5 itself and the vessel wall of the concentration vessel 1.

[0053] In a preferred embodiment, when the residual liquid level in the concentration vessel 1 reaches a second preset height, the environmental pressure inside the concentration vessel 1 is controlled to reach a second preset pressure value, which is greater than the first preset pressure value. Specifically, the second preset pressure value is a positive pressure value. In a specific embodiment, the second preset pressure value is 0.05MPa to 0.15MPa, so that the residue and concentrate in the concentration vessel 1 can be smoothly discharged by using positive pressure.

[0054] The total height of the internal containment space of the concentration vessel 1 is defined as L. The aforementioned first preset height is 80%L, and the aforementioned liquid level value is the single recovery processing capacity. The larger the processing capacity, the higher the efficiency. Experiments have shown that at a liquid level of 80%, overflow will not occur and the processing efficiency is the highest. The aforementioned second preset height is 10%L. At this point, the residual liquid has a relatively large solid content and a relatively small liquid volume. At this point, the introduction of demineralized water can more effectively dissolve the dimethyl sulfoxide adhering to the residue, resulting in more thorough cleaning and ensuring the recovery rate of dimethyl sulfoxide.

[0055] See Figure 4 As shown, a control relationship curve between the rotational speed of the stirrer 5 and the real-time residual liquid level is presented. Specifically, the first rotational speed of the stirrer 5 is defined as V, which is also the maximum operating speed of the drive motor of the stirrer 5. The real-time residual liquid level in the concentration vessel 1 is Ls (i.e., Figure 4 (The liquid level value in the liquid). When 70%L < Ls ≤ 80%L, the stirrer 5 rotates at a constant speed of V to ensure that the dimethyl sulfoxide in the residual liquid evaporates to the maximum extent and to ensure concentration efficiency. Understandably, the viscosity of the residual liquid is low at this time, and a higher speed will not be detrimental to the stirrer 5. When 50%L < Ls ≤ 70%L, the speed of the stirrer 5 is linearly reduced from V to 50%V. When 20%L < Ls ≤ 50%L, the speed of the stirrer 5 is linearly reduced from 50%V to 10%V. In this stage, the solid content of the residual liquid gradually increases, and the viscosity also increases accordingly. Appropriately reducing the stirring speed of the stirrer 5 is beneficial to both preventing damage to the stirrer 5 and improving the higher recycling efficiency (i.e., concentration efficiency). When 10%L < Ls ≤ 20%L, the stirrer 5 rotates at a constant speed of 10%V. In this stage, the lower stirring speed can provide a certain driving effect for slag and liquid discharge, making slag and liquid discharge smoother. As a preferred embodiment, the rate of decrease in the rotational speed of stirrer 5 when 50%L < L1 ≤ 80%L is greater than the rate of decrease in the rotational speed of stirrer 5 when 20%L < L2 ≤ 50%L, that is... Figure 4 In the range of 50%L < L1 ≤ 80%L, the slope of the straight line is greater than that in the range of 20%L < L2 ≤ 50%L. This allows for smoother speed changes during the stage when the residual liquid has a high solid content, reducing the possibility of damage to the stirrer 5 and its drive motor.

[0056] It should be noted that the rotation speed of the stirrer 5 in this invention is adjusted based on the relative relationship between the real-time liquid level Ls of the residual liquid and the total height L of the internal containment space of the concentration vessel 1. This relative relationship of liquid level height has a certain correspondence with the solid content or viscosity of the residual liquid. This correspondence can be obtained by detection. This technical solution does not use an online detection method for solid content or viscosity, which simplifies the control strategy and saves system design costs.

[0057] Verification showed that the recovery rate of dimethyl sulfoxide (DMSO) was relatively high when the first rotational speed was 100 rpm to 150 rpm, as shown in the table below. The recovery rate of DMSO increased with increasing first rotational speed. Corresponding to the first rotational speed, the second rotational speed was 10 rpm to 15 rpm. As shown in the table below, the preferred first rotational speed was 150 rpm, and the preferred second rotational speed was 15 rpm.

[0058]

[0059]

[0060] As can be seen from the table above, the recovery rate no longer increases above 150 rpm, which objectively increases energy consumption. Below 100 rpm, the recovery rate decreases within the same processing time.

[0061] The aforementioned first preset pressure value, i.e., the vacuum pressure, is 4 kPaA to 10 kPaA. The distillation residue consists of dimethyl sulfoxide, decomposition products, inorganic salts, polymers, etc., and has a high boiling point. If the vacuum degree is greater than 10 kPaA, the higher the temperature, the more likely the distillation residue will undergo further decomposition and cracking, potentially causing a safety accident. If the vacuum degree is less than 4 kPaA, some decomposition products will evaporate simultaneously with dimethyl sulfoxide, reducing the separation efficiency. Therefore, this invention uses a relatively low vacuum degree to achieve the evaporation and separation of dimethyl sulfoxide, while concentrating the remaining heavy components. The first preset temperature is 90℃ to 120℃, ensuring that dimethyl sulfoxide evaporates into the gas phase while preventing further decomposition and cracking of the distillation residue, which could lead to explosions or other accidents.

[0062] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for recovering dimethyl sulfoxide distillation residue, characterized in that, The method employs a dimethyl sulfoxide (DMSO) distillation residue recovery system, which includes: a concentration vessel (1) containing a stirrer (5), the concentration vessel (1) having a feed inlet (13), a vapor phase outlet (11), and a waste discharge pipe (12), wherein the feed inlet (13) is connected to the residue outlet of the DMSO distillation vessel, the waste discharge pipe (12) having a slag outlet (121) and a first liquid outlet (122), the waste discharge pipe (12) being located at the bottom of the concentration vessel (1), the waste discharge pipe (12) being vertically arranged, the slag outlet (121) being located at the bottom end of the waste discharge pipe (12), and the first liquid outlet (122) being located on the side wall of the waste discharge pipe (12); and an evaporator-condenser (2) connected to the vapor phase outlet (11). The gaseous dimethyl sulfoxide discharged from the concentration vessel (1) is condensed and liquefied, and has a second drain port (21); a condensate collection tank (3) is connected to the first drain port (122) and the second drain port (21), the dimethyl sulfoxide volatilized in the concentration vessel (1) is recovered to the condensate collection tank (3) through the gas phase discharge port (11), the concentrate containing dimethyl sulfoxide after solid-liquid separation is recovered to the condensate collection tank (3) through the first drain port (122), and the solid, harmless residue after solid-liquid separation is discharged through the slag discharge port (121); the condensate collection tank (3) has a third drain port (31), the third drain port (31) is used to connect a pumping component to pump the condensate collected in the condensate collection tank (3) to the dimethyl sulfoxide distillation vessel; The method includes: The residual liquid from the dimethyl sulfoxide distillation vessel is transferred to the concentration vessel (1), and the injection is stopped when the residual liquid level reaches the first preset height. Control the vacuum level of the environment inside the concentration vessel (1) to reach the first preset pressure value and the temperature to be at the first preset temperature; Control the stirrer (5) to rotate at a first speed; When the residual liquid level in the concentration vessel (1) drops to the second preset height, demineralized water is introduced into the concentration vessel (1) to separate the residual liquid into solid and liquid residue and concentrate. After opening the slag discharge port (121) to discharge the residue, open the first liquid discharge port (122) to discharge the concentrate into the condensate collection tank (3).

2. The method for recovering dimethyl sulfoxide distillation residue according to claim 1, characterized in that, As the residual liquid level in the concentration vessel (1) decreases, the rotation speed of the stirrer (5) is reduced to a second rotation speed; and / or, when the condensate collection tank (3) has a third drain port (31) and a pumping component is connected between the third drain port (31) and the dimethyl sulfoxide distillation vessel, the pumping component is controlled to operate after the concentrated liquid is discharged into the condensate collection tank (3); and / or, when the residual liquid level in the concentration vessel (1) reaches a second preset height, the environmental pressure inside the concentration vessel (1) is controlled to increase to a second preset pressure value.

3. The method for recovering dimethyl sulfoxide distillation residue according to claim 2, characterized in that, The total height of the internal space of the concentration vessel (1) is L, the first rotation speed of the stirrer (5) is V, the real-time liquid level of the residual liquid in the concentration vessel (1) is Ls, when 70%L < Ls ≤ 80%L, the stirrer (5) rotates at a constant speed of V, when 50%L < Ls ≤ 70%L, the rotation speed of the stirrer (5) decreases linearly from V to 50%V, when 20%L < Ls ≤ 50%L, the rotation speed of the stirrer (5) decreases linearly from 50%V to 10%V, and when 10%L < Ls ≤ 20%L, the stirrer (5) rotates at a constant speed of 10%V.

4. The method for recovering dimethyl sulfoxide distillation residue according to claim 3, characterized in that, The first preset pressure value is 4 kPaA~10 kPaA, the first preset temperature is 90℃~120℃, and the second preset pressure value is 0.05 MPa~0.15 MPa; and / or, the first rotation speed is 100 rpm~150 rpm, and the second rotation speed is 10 rpm~15 rpm; and / or, the rotation speed reduction rate of the stirrer (5) when 50%L < L1 ≤ 80%L is greater than the rotation speed reduction rate of the stirrer (5) when 20%L < L2 ≤ 50%L; and / or, the first preset height is 80%L, and the second preset height is 10%L.

5. The method for recovering dimethyl sulfoxide distillation residue according to claim 1, characterized in that, It also includes a vacuum pump (4), which is connected to the evaporator-condenser (2).

6. The method for recovering dimethyl sulfoxide distillation residue according to claim 5, characterized in that, The bottom of the concentration vessel (1) is an inverted cone, and the waste discharge pipe (12) is located at the top of the cone.

7. The method for recovering dimethyl sulfoxide distillation residue according to claim 6, characterized in that, The stirrer (5) includes a stirring frame (51) whose bottom shape matches the shape of the bottom of the vessel.

8. The method for recovering dimethyl sulfoxide distillation residue according to claim 7, characterized in that, The stirring frame (51) is provided with a plurality of scrapers (52) at a position corresponding to the wall of the concentration vessel (1), the distance between the scraper (52) and the vessel wall is not greater than 50mm; and / or, the scraper (52) is detachably connected to the stirring frame (51); and / or, the scraper (52) is made of stainless steel or polytetrafluoroethylene.

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